Making red phosphorus



Patented Apr. 9, 1946 MAKING RED PHOSPHORUS Thomas W. De Witt, Florence, Ala., assignor to Tennessee Valley Authority, a corporation of the United States No Drawing.

' 7 Claims.

amended Apr-il so, 1928;. 370 o. G. 151) The invention herein described may be manufactured and used by error the Government for governmental purposes without the "payment to me of any royalty thereon. F

This invention relates to the'art of converting yellow phosphorus into red phosphorus.

The principal object ofthis invention is to produce a finely divided red phosphorus without the necessity of disintegrating agglomerated material ordinarily produced during the conversion from yellow phosphorus. Another object of this invention is to provide a continuous method for the production of red phosphorus of prime grade. Other objects of this invention include the provision of an economical method for the manufacture of red phosphorus from yellow phosphorus whereby the overall time required for the carrying out of all thesteps thereof is materially reduced. I I

In the commercial manufacture of red phosphorus, liquid yellow phosphorus is heated in a large converter for some three to five days. The solid product is then removed from the converter, ground and leached with a suitable-solvent to remove traces of unconverted yellow phosphorus. In such an operation, catalysts such as iodine,

Application October 25, 1M3, Serial No. 507,606 a (Granted under the act of March 3, 1883, as

ing continued until the conversion to fifty percent completion. The mixture of red phosphorus and yellow phosphorus was withdrawn from the converter and charged into a vacuum still fitted with an agitator. The disintegration was carried on until all of the yellow phosphorus in the mixture had been removed.

The red phosphorus obtained thereby was in the form of soft friable lumps with the majority of the material havlngapart'icle size of 30 to 80 microns. The rate of conversion of yellow phosphorus to red phosphorus becomes appreciable at.

go phorus. The principal feature of the present inbromine, oxides of nitrogen, selenium, r sulfur for making red phosphorus by heating molten yellow phosphorus at a conversion temperature vention is the carrying out of this conversion only so far to at all times have the resulting mixture of red and yellow phosphorus in a fluid condition; However, at the same time, it is obviously desirable to have as high a conversion as possible and still maintain this condition. A converted mixture may have a fair fluidity with six ty per cent of converted red phosphorus therein,

carried on but still maintain a fluid condition in and for a length of time such that a substantial particles of red phosphorus takes place. Anex ample of the production of red phosphorus ac- 50- cording to the present invention is given below. Yellow phosphorus was charged into a converter equipped with a reflux and previously freed from an oxidizing'atmosphere. The yellow phosphothe mixture. mately 1% of sulfur as a catalyst resultsin the production of a mixture with the approximate permissible fluidity with only about forty per cent-conversion of the yellow phosphorus ,to red phosphorus. The converted mixture then not only has a constituency suitable for relatively easy transfer to subsequent steps in the process, but is also particularly suitable for handling according to one specific step, namely, that of sep- 5' aration of red phosphorus therefrom by sedimen- 4 I tation.

Since the reaction involved in the conversion of yellow'phosphorus toi'red phosphorus is exothermic, it is imperative that the conversion temperature be accurately controlled. This is readily accomplished by carrying out the conversion under refluxing conditions. For the simplest operation of the present invention, it is preferable to carry out the conversion at the temperature of the boiling point of phosphorus under atmosms was heated to its boiling point and the 'heatas pheric pressure, The time requir d for y P was carried For example, the use of approxi- C. in the absence of catperature effective to convert the yellow phos- For more ef- 'phorus to red phosphorus, (b) discontinuing said cent conversion at 280 heating operation while the proportion of yellow alyst is of the order of 6 hours. festive conversion in a shorter time, it is there fore p he ecojhonli a to to red phosphorus is such that the cerrfouif'ihe convers on um'i "ratmsfp rie 5 flue" tihe pyessure pressures, ut still carryingout the operation we. and temperature of co si he! (c) sepaedrto-I rating the unconverted yellow phosphorus from der conditions such that refluxing is employ control the reaction. I of 300 C. and 320 C. and V pressures of 1.46 and 2 zosz etniospheres, e tively, reduced the time requirect' iors n cent conversion of yellow phosphorus to phosphorus to approximately v r ty minutes, respectively. Th "conv yellow phosphorus to red phospholjls suhsequentseparation of the yellovf'p from the red Dhosphoru'suna' a converter equipped with i-Io ev the red phosphorus in the mixture in such fluent assume; without any appreciable further ,con-

iioyv phosphorus runto red phos- 13 making red phosphorus which eating moiten yellow phosphorus e n w tire efifective to convert the yellow sphorus to red phosphorus, (b) discontinuing iii" heating operation while the proportion of ilow ghosohorus to red phosphorus is such that iie fiuemeondition at the pressure and temperature of conversion, (c) removing *ahefl 1 fluent mixture? re rig e'" phOSph us which eliowzphosphorus --"@the; yellow discontinuhospliorusis such 'con iition at the river sioniflc) reidi heatingeoperatiqn -vvhen of the yellow'phosphorus has been no themixtureis W k s? appuecialbles-zrfurther conversi ihosphorussrunrabo e 94 32 K? process ofamekins oomprisessiaagsheating mo en undeh ia-supeneatmospheri v 

